function Sphere(mass,x,y,spX,spY,isFix){
	//固定
	this.isFix=isFix?isFix:false;
	
	//半径
	this.radius=3;
	
	//质量
	this.mass=mass;
	
	//颜色
	this.color='#000';
	
	//位置
	this.x=x;
	this.y=y;
	
	//速度
	this.spX=spX;
	this.spY=spY;
	
	/*//加速度
	this.accX=0;
	this.accY=0;*/
	
	this.draw=function(ctx){
		ctx.beginPath();
		ctx.fillStyle = this.color;  
        ctx.arc(this.x, this.y, this.radius+this.mass/500, 0, 2*Math.PI, false);  
        ctx.closePath(); 
        ctx.fill();
        ctx.fillText("("+this.x.toFixed(0)+","+this.y.toFixed(2)+")",this.x+4,this.y);
	};
	
	this.move=function(accX,accY){
		this.spX+=accX;
		this.spY+=accY;
		this.x+=this.spX;
		this.y+=this.spY;
		//console.log(this.spX+" "+this.spY+" "+accX+" "+accY);
	};
}
